The present invention relates to a LED lamp unit comprising at least two LED light sources arranged on two opposing sides of a support member to emit in opposed half-spaces, a heat sink in thermal contact with said support member of the LED light sources and an electrical connector socket for electrically connecting the LED light sources. The invention also relates to a headlamp at least comprising a reflector, a H4 lamp holder and such a LED lamp unit.
Automotive H4 halogen bulbs provide low and high beam from a single light source having two filaments. The corresponding headlamp is designed to provide a low beam reflector and a high beam reflector as well as the corresponding lamp holder for mounting the H4 bulb in the appropriate position and orientation. Due to the cost efficient H4 headlamp concept this technology is still the most popular light sources technology for low and medium car segments.
The main drawback of halogen bulb technology is its inefficiency and limited lifetime. Additionally it is often extremely difficult to exchange the bulb without the help of a garage. In order to provide an acceptable light distribution which is compliant to the corresponding legal regulations a H4 bulb requires a power of 60 W to generate a flux of 1000 lumen. The corresponding typical lifetime is on the order of 500 hours.
On the other hand LED technology is much more energy efficient and provides a lifetime which is equal to a car life. A few years ago the first Full-LED-headlamps were launched mainly in the high end car segments. All these headlamps had to be equipped with optics which are optimized to the corresponding LED light emission pattern in order to fulfill the legal beam pattern requirement.
It is desirable to provide so called LED retrofits which may simply replace the known H4 halogen bulbs in an automotive headlamp without any change in the design of the optics of the headlamp. At present LED retrofits for nearly every automotive halogen bulb type a available in the market which fit into the corresponding lamp holder of the halogen headlamps. These commercially available LED retrofits however, at least in case of H4 LED retrofits, provide excessive glare and only 10% of the illumination values required for a legal beam pattern.
Such H4 retrofit LED lamp is for instance disclosed in DE 10 2007 044 628. The retrofit LED lamp is provided with LED light sources arranged on two opposing sides of a support member and may emit light in two opposing half-spaces. Also thermal conducting elements are provided. The retrofit LED lamp is further provided with a connector for mounting the lamp in the holder of a headlamp.
The known H4 retrofit LED lamps do not fulfill the legal beam pattern requirement without a change of the optics of the headlamp.